This R13 application supports the Fourth International Meeting of the International Society for Extracellular Vesicles (ISEV) to be held at the Bethesda North Marriott from April 22-26, 2015. The meeting Extracellular Vesicles : translating basic science to address human disease will bring together American clinicians from the Baltimore/Washington medical and biotechnology communities to translate to clinical care the work of the 700 basic scientists of ISEV. Extracellular Vesicles (EV, including exosomes, microvesicles, apoptotic bodies, and others) range in diameter from 30 nm to one micron and containing proteins, lipids, RNA, and metabolites derived from the cell of origin. EV act locally i tissues but are also secreted into and can be purified from biofluids. ISEV 2015 will address immune regulation, HIV/AIDS, antigen presentation, coagulation, tissue remodeling, the role of EV in cancer metastasis, diagnosis and prognosis as carriers of tumor-specific protein and RNA mutations, and delivery of therapies. The meeting will begin with an Educational Day, April 22, on isolation of EV from clinical samples, in cooperation with the NIH Common Fund Extracellular RNA Communication Consortium. The Educational Day will feature oral presentations as well as technical workshops led by academic and industry representatives. The main meeting, from April 23-26, will witness a keynote speech by 2013 Nobel Laureate James Rothman. Francis Collins of NIH and EV pioneer Xandra Breakefield of Harvard have also been invited as plenary speakers. Three parallel oral sessions will take place, with a total o 27 thematic sessios, will address pressing issues in EV and medical research. A distinguished international panel, including the editors of ISEV's Journal of Extracellular Vesicles and DC-area researchers, will review submitted abstracts for assign more than 100 oral presentations and 300 thematically-grouped posters. Accessibility and service to underrepresented minorities, women, and young and early stage investigators are priorities. The Educational Day and plenary sessions will be web-broadcast to medical students, researchers in allied fields and underrepresented minority institutions. ISEV plans to provide fifteen traveling fellowships to members of underrepresented minority groups and young investigators. The Conference Center is fully accessible and ADA compliant. A dedicated room will be set up for nursing mothers, and information about daycare options for children or dependent seniors will be offered on the ISEV website and on-site. The ISEV 2015 meeting and the R13 that supports it will host 750-1000 attendees and emphasize consensus standards by which to define and isolate EV and their subtypes; strive for agreements on preparative and isolation techniques and normative specimen biorepositories; and strengthen existing consortia and establish new partnerships for biomarker validation and treatment studies in oncology and infectious diseases, among others. No other meeting offers the scope and participation of ISEV 2015 to address timely questions in the EV field. ISEV 2015 provides an opportunity to combine the international intensity of ISEV's basic and clinical scientists with the vibrant and growing American community of EV investigators in what will surely be the most influential event of 2015 in the EV field.